KR20140020265A - Process for separation of water from pyrolysis gasoline - Google Patents

Abstract

The method of separating water from pyrolysis gasoline obtained from the steam cracking step uses a water separator coalescer. And the apparatus includes a coalescer for separating water from pyrolysis gasoline.

Description

Separation of water from pyrolysis gasoline {PROCESS FOR SEPARATION OF WATER FROM PYROLYSIS GASOLINE}

The present invention relates to a method for separating water from pyrolysis gasoline obtained from a steam cracking step using a water separation coalescer. The invention also relates to an apparatus comprising a coalescer for separating water from pyrolysis gasoline.

Coalescers are a technical device for performing coalescence. Coalescers are mainly used to separate two liquid phase systems, such as dispersions or preferably emulsions, into their components through various processes. Coalescers work against emulsifiers. In addition to commonly used electronic coalescers, one major group of coalescers is mechanical coalescers. Mechanical coalescers use surfaces to which droplets coalesce. Typically used instruments are filter cartridges, net material or containers with different fillings. The use of mechanical coalescers is described, for example, in Siemens Miltronics Process Instruments Inc., Case Study, 2006 and in Chem.-Ing.-Tech., 1976, No 3, pages 177 to 189.

Steam cracking is a petrochemical process that breaks down saturated hydrocarbons into smaller, usually unsaturated, hydrocarbons. Steam cracking is a major industrial method for producing lighter olefins, such as ethylene and propylene, for example as disclosed in EP-A 1 302 525. Pyrolysis gasoline is a typical product that can be obtained from steam cracking processes. However, pyrolysis gasoline may also be regarded as an intermediate, since the gasoline is usually subjected to additional process steps, for example hydrogenation and / or separation into its components.

H.-M. Allmann et al. (29 pages in total), presented at the DGMK-Conference “Selective Hydrogenation and Dehydrogenation,” November 12, 1993, in Kassel, Germany. Provides an overview of hydrogenation and purification. However, the paper is silent about the presence of water during the steam cracking process or the following purification and hydrogenation steps.

If (free) water is present in the organic pyrolysis gasoline stream, the hydrogenation catalyst may be partially or fully deactivated. In general, the activity and lifetime of a fixed bed catalyst for pyrolysis gasoline hydrogenation varies with the amount of water in contact with the catalyst surface. Thus, the presence of water in the pyrolysis gasoline stream has the result that the number of turnovers associated with the activity of the hydrogenation catalyst is reduced and the hydrogenation catalyst needs to be regenerated more frequently. This means economic and environmental shortcomings. In addition, the small amount of water cannot be separated by conventional methods, for example by phase separation by gravity, since the amount of water is distributed into droplets in the pyrolysis gasoline stream. Also, for example, methods such as distillation are ineffective in reducing the amount of water in the pyrolysis gasoline obtained from the steam cracking step.

Lee Siang Hua's paper ["Titan's Experience in Physical Separation Devices"] prepared for the 15th Symposium of Chemical Engineers at the Hyatt Hotel in Johor Bahru, Malaysia, on September 12, 2001. Provides an overview of the separation apparatus used, for example, to remove water from the stream of organic compounds obtained from the steam cracking process. Four different types of physical separation devices are discussed. In order to perform liquid-liquid separation, the operation may be based on gravity separation or coalescence separation in an oil-water coalescer to separate dissolved hydrocarbons in cooling water or to remove water from raw pyrolysis gasoline. Such coalescing separation can be used, where small particles in one liquid phase must be separated or removed from a large amount of the other liquid phase. The disclosed coalescer is a wire mesh coalescer contained in a horizontal container.

Pall Corporation's paper Liquid / Liquid coalescer applications: Ethylene processing-dilution steam system, edited in 1997 (2 pages in total) discloses a process for obtaining ethylene from pyrolysis gasoline. A total of four coalescers are used for different purposes at different locations in the ethylene process. For example, one coalescer is used to remove gasoline from water out of the first stream obtained from the oil / water separator. Another coalescer is used to remove water from gasoline out of the second stream obtained from the oil / water separator. However, the arm corporation paper is silent on the material of the coalescer.

It is an object of the present invention, in particular, to provide a method for the efficient separation of water from pyrolysis gasoline obtained from the steam cracking step in order to remove the remaining water remaining after a conventional phase separation step.

The problem of the present invention is solved by providing a method for reducing the water content in pyrolysis gasoline obtained from the steam cracking step, wherein the method separates water from the pyrolysis gasoline via one or more coalescers, and the apparatus comprises a metal, fiber glass or It is characterized in that it is made of a combination of metal and fiber glass.

The advantage of using coalescers made of metal and / or fiber glass to remove water from pyrolysis gasoline obtained from the steam cracking step is that water can be removed very efficiently. The total water content in the pyrolysis gasoline stream is the sum of dissolved water and entrained water. Only the entrained water can be removed from the pyrolysis gasoline by coalescence. This advantage is even more pronounced when using the coalescer after a conventional phase separation step to remove the main amount of water.

Moreover, when a coalescer is used before the hydrogenation step, the hydrogenation step has a higher conversion. Thus, the hydrogenation catalyst has a longer life since it requires less frequent regeneration. In addition, the chemical structure of the catalyst is changed by the accompanying water, which is prevented by water separation before hydrogenation.

Often, a stream from a partially hydrogenated pyrolysis gasoline or reformer purchased is mixed with the pyrolysis gasoline prior to the secondary hydrogenation step. In this case, the water separation before the hydrogenation step provides the advantage of protecting the catalyst similar to the separation before the first hydrogenation step.

1 shows coalescer screening for feed pyrolysis gasoline.
2 shows coalescer selection for partially hydrogenated pyrolysis gasoline.

In the following, the method according to the invention is explained in more detail.

The term "coalescer" within the context of the present invention refers to any mechanism or device that can be used to perform coalescing, such as coalescing steps or coalescing separation. The coalescer may be integrated into or part of a larger unit, for example a housing or a container. The larger unit may contain, in addition to the coalescer, additional devices, for example prefilters, pipes, inlets, outlets or separators. Such further devices are usually connected to each other and to the coalescer by, for example, the pipe. However, the additional devices are not considered to be part of the coalescer within the context of the present invention.

The coalescer used to separate the water from the pyrolysis gasoline to reduce the water content can be any type of coalescer known to those skilled in the art. Preferably, the coalescer is an coalescing filter cartridge, coalescing filter or coalescing tube.

The coalescer is produced as a metal, fiber glass or a combination of metal and fiber glass. Preferably, the coalescer is produced as a metal or a combination of metal and fiber glass. More preferably, the coalescer is made of metal. Coalescers made from a combination of metal and fiberglass are also termed composite or composite candles. In the case where the coalescer is made of fiber glass, it is preferable to use fiber glass having a pore diameter (fineness) of ≧ 40 μm. In case the coalescer is made of metal, the metal is preferably stainless steel.

The term "manufactured" within the context of the present invention means that the materials used to produce the coalescers each contain metal or fiber glass. However, the material used may contain other components in addition to the metal or fiber glass. Preferably, the materials used contain up to 50% or more, more preferably up to 75% or more, of metal or fiber glass, respectively. Coalescers made as a combination of metal and fiberglass mean that some parts of each of these coalescers are made of metal, while others are made of fiberglass. However, the material used may contain other components in addition to the metal and fiber glass. For clarity, it is indicated that the material can be used to produce any type of coalescer as defined above, for example coalescing filters or coalescing tubes.

Within the process of the invention, one or more coalescers made of metal, fiber glass or combinations thereof are used. However, additional coalescers made of different materials besides metal or fiber glass may also be used further in the process of the invention. Said further coalescer is for example made of cotton, acrylic / phenolic resin or wire mesh. In the following, particular examples are given of coalescers made of different materials besides any materials, in particular metal or fiberglass.

Steam cracking processes or steam cracking steps to obtain pyrolysis gasoline are known to those skilled in the art. Pyrolysis gasoline used in the process according to the invention is also known to those skilled in the art. Suitable examples of pyrolysis gasoline used in the process of the invention can be found, for example, in the paper of H. M. Olman et al. In the previously mentioned DGMK-Conference 1993. The pyrolysis gasoline preferably contains hydrocarbons having 5 or more carbon atoms ("C ₅ ⁺ -cut"). Preferred pyrolysis gasoline comprises 29 to 36 wt% benzene, 14 to 19 wt% toluene, 3 to 7 wt% xylene, up to 1.5 wt% butadiene and additional components. Examples of additional components are ethylbenzene, styrene, 1,2,3,4-tetrahydronaphthene, indene, vinyltoluene, n-hexane, 2-methyl-1,3-butadiene, isopentane, pentane And / or naphthene.

The pyrolysis gasoline obtained from the steam cracking process may contain water in an amount up to about 1.2 kg water / kg pyrolysis gasoline. The pyrolysis gasoline mixture (with water) is preferably obtained from the quenching step, which mixture may be a dispersion of pyrolysis gasoline in water or vice versa.

If the pyrolysis gasoline contains a larger amount of water, for example more than 3% by weight of water (relative to the amount of hydrocarbons), one or more additional water separation steps may be carried out prior to water separation by use of the coalescer. It is preferable to carry out.

In a preferred embodiment, the coalescer is used after a phase separation step (also referred to as the main phase separation step) in which the main phase water is separated from the pyrolysis gasoline.

It is advantageous with regard to economic and environmental criteria to use the coalescer immediately after the phase separation step. In this step, the pyrolysis gasoline stream is usually pure and not diluted with additional streams from pyrolysis gasoline stripping and debutulization, the streams being subjected to primary hydrogenation prior to the hydrogenation step, preferably as described below. It may optionally be added immediately before the step.

This phase separation step is usually carried out by gravity separation in a (normal) phase separation unit. Such phase separation units are known to those skilled in the art, depending on the scale of the process. Preferred phase separation units are selected from the group comprising fillers or fillers, nets, centrifuges, separators or settler with membranes, vessels and columns.

After the phase separation step, the pyrolysis gasoline phase still contains a small amount of water. The pyrolysis gasoline phase may contain up to 3% by weight of water after the phase separation step, preferably 0.3 to 2.5% by weight of water after the phase separation step.

In a preferred embodiment of the invention, the coalescer is used before the hydrogenation step (preferably primary hydrogenation step). Even more preferably, the coalescer is used after the phase separation step and before the hydrogenation step, in particular before the primary hydrogenation step. If the coalescer is used before the primary hydrogenation step, further coalescers may be used after the primary hydrogenation step, for example before the secondary hydrogenation step.

Instead of using the coalescer after the first hydrogenation step and before the secondary hydrogenation step without the coalescer before the first hydrogenation step, the advantage of using the coalescer before the first hydrogenation step is that the primary hydrogenation catalyst Premature loss of catalysis can be prevented.

The coalescer may further contain a filler material. The filler material can be independently a metal, fiber glass, plastic or ceramic or any other material known to the skilled person. Preferably, the filler material is made of the same material as the coalescer. Preferred materials are therefore metals, fiberglass or combinations thereof, in particular metals. If more than one coalescer is used, the filler material for each coalescer used may be selected independently. Preferably each coalesce used contains a metal as filler material.

In a preferred embodiment of the invention, water separation in the coalescer is carried out at a temperature of ≦ 40 ° C. of the pyrolysis gasoline. Preferably, the embodiment is carried out in a coalescer placed before the first hydrogenation step. More preferable temperature range is 20-40 degreeC. A temperature of ≦ 40 ° C. can be obtained by cooling the pyrolysis gasoline before entering the coalescer. Preferably, the pyrolysis gasoline is cooled from a temperature of at least 80 ° C to a temperature of ≤ 40 ° C. If more than one coalescer is used, it is desirable to have the above conditions in each coalescer used.

In one embodiment of the invention, a prefilter may be used before at least one coalescer, preferably before the coalescer used prior to the first hydrogenation step. Prefilters are known to those skilled in the art. For example, a solid prefilter can be used.

Another preferred embodiment of the present invention is a steam cracking process for separating water from pyrolysis gasoline, wherein the process

(a) quenching the pyrolysis gasoline mixture;

(b) phase separation from the pyrolysis gasoline by separation of the main phase water;

(c) causing the pyrolysis gasoline to contain up to 3% by weight of water through the coalescer;

(d) subjecting the hydrogenation stage to pyrolysis gasoline without entrained water;

/ RTI >

The conditions for carrying out the hydrogenation steps according to the process of the invention and the catalysts used are known to those skilled in the art. Processes for the selective hydrogenation of unsaturated hydrocarbons are disclosed, for example, in EP-A 0 885 273, EP-A 0 881 275, EP-A 1 302 525 and DE-A 19911094. Catalysts for the selective hydrogenation of pyrolysis gasoline are for example disclosed in WO-A 2008/138785. Special devices (eg hydrogenation units) for the selective hydrogenation of such pyrolysis gasoline are disclosed for example in DE-A 19911094.

In one embodiment of the present invention, the process is carried out by two hydrogenation steps, wherein the pyrolysis gasoline is hydrogenated. For the first liquid phase hydrogenation step, alumina-based palladium or nickel fixed bed catalysts are usually used. Prior to the first liquid hydrogenation step, the pyrolysis gasoline stream may optionally be mixed with further streams from pyrolysis gasoline stripping and / or debutulization.

In the first stage hydrogenation, mainly dienes and styrene are hydrogenated. The product of this hydrogenation step is called partially hydrogenated pyrolysis gasoline. In the secondary hydrogenation step, most of the remaining double bonds are hydrogenated and hydrodesulfurization is carried out. The second stage hydrogenation is usually carried out in the gas phase on an alumina cobalt / molybdenum or nickel / molybdenum catalyst. Liquid hydrogenation is also possible.

As indicated above, more than one coalescer and / or coalescer made of different materials other than metal or fiberglass can be used in the process according to the invention. If two or more coalescers are used, it is preferred to use one coalescer before the primary hydrogenation step and one coalescer before the secondary hydrogenation step. Preferably both coalescers are made of metal, fiberglass or a combination thereof.

In a preferred embodiment of the invention two coalescers (A) and (B) are used in the process of the invention. The coalescer (A) is made of metal, fiber glass or a combination thereof as defined above. In contrast to the coalescer (A), the coalescer (B) can be any coalescer known to those skilled in the art. Preferably the coalescer (B) is an coalescing filter cartridge, coalescing filter or coalescing tube.

The coalescer (B) may be made of any substance or mixture of substances known to those skilled in the art. Preferably, the coalescer (B) is made of metal, composite, fiber glass, wire mesh, cotton or acrylic / phenolic resin. A more preferable substance for the coalescer (B) is a metal. The term "manufactured" in connection with coalescer (B) has the same meaning as defined above in connection with coalescer (A). Preference is given to using each of the above substances in each case in an amount of at least 50% by weight.

Within this embodiment, the coalescer (A) is used after the main phase separation step and before the primary hydrogenation step, while the coalescer (B) is used after the primary hydrogenation step and before the secondary hydrogenation step. It is even more preferred that the coalescer (A) is made of metal, fiber glass or a combination thereof and the coalescer (B) is made of metal. Most preferably both coalescers (A) and (B) are made of metal. It is also preferred that both the coalescers (A) and (B) contain a filler material, and that the material is made of the same material as the respective coalescers.

In another preferred embodiment, the coalescer (B) is used after the main phase separation step and before the primary hydrogenation step, while the coalescer (A) is used after the primary hydrogenation step and before the secondary hydrogenation step. . Within this preferred embodiment the coalescer (A) is preferably made of metal. It is also preferred that both the coalescers (A) and (B) contain a filler material, and that the material is made of the same material as the respective coalescers.

One or more additional streams may be added to the pyrolysis gasoline stream according to the invention. The additional streams may be independently of one another, for example streams obtained from partially hydrogenated pyrolysis gasoline or reformers. Said additional streams are preferably added if two coalescers are used in the process of the invention.

More preferably, at least one, in particular one additional stream is added after the first hydrogenation step and before the coalescer, which in turn is used before the secondary hydrogenation step.

Another subject of the invention is an apparatus comprising at least one coalescer, a water separation unit and at least one hydrogenation unit made of metal, fiber glass or a combination of metal and fiber glass. The apparatus can be used to carry out the method of the invention as described above.

The water separation unit for phase separation can be any separation unit known to those skilled in the art. Examples for separation units are fill or filler, nets, centrifuges, settler with separator or membrane, vessel or column.

Hydrogenation units are known to those skilled in the art. Usually, the hydrogenation unit is pressure resistant reactors depending on the scale of the reaction and the required pressure.

In one embodiment of the invention, the water separation unit is connected to the coalescer (A) and the coalescer (A) is connected to a primary hydrogenation unit, which in turn is followed by the coalescer (B). Connected to a secondary hydrogen unit, wherein the coalescer (A) and / or coalescer (B) is made of metal, fiber glass or a combination of metal and fiber glass.

Another subject of the present invention is the use of the aforementioned device for the water separation of pyrolysis gasoline. The use of the device in which the coalescer is made of metal is preferred.

Example

Coalescer Screening

Phase separation of the system is strongly determined by coalescence. In order to determine the most suitable coalescer material, coalescer selection is carried out with steam cracker product at 40 ° C. and 0.4% by weight aqueous phase. During the selection of possible coalescing cartridge materials, the maximum load [kg / cm 2 h] through the coalescer cartridge without entrained water is also measured for each material.

In coalescer screening, experimental scale stirred vessels are used to produce 0.4 wt% water in the pyrolysis gasoline dispersion. The dispersion is pumped through a small piece of filter cartridge starting with a small load. The flow direction is from the inside of the filter cartridge toward the outside through the cartridge network. The filter cartridge is fixed in a small glass container in the inlet tube. By raising the load through the cartridge at one characteristic point, the pyrolysis gasoline changes from transparent to turbid. At this point the water content of the spilled pyrolysis gasoline is higher than the solubility of 750 ppm (40 ° C.). During the experiment (during load rise) the turbidity is observed and the water content of the sample is assessed by Karl-Fischer-titration.

The coalescing cartridge materials are tested according to Table 1 below and the results of each can be seen in FIG. 1 or 2 respectively:

matter manufacturer metal Franken Combination of Metal and Fiber Glass (Composite) Faudi (P type) fiber glass Fuhr if AMA Acrylic / phenolic resin Cuno

For fiber glass, two mesh sizes 25 μm and 50 μm are tested.

1 shows the total water content according to the mass flow through the cartridge. The 750 ppm line corresponds to water solubility for pyrolysis gasoline at 40 ° C. and is therefore the baseline (“dissolved water”). The water concentration also rises at one point as the load is increased for each material. These characteristic points allow the materials to be evaluated. The higher the maximum mass flow value, the better the material.

The total water content is the sum of the water accompanied with the dissolved water. Only entrained water can be removed from the pyrolysis gasoline by coalescence.

The metal and composite candles exhibit the best coalescence performance at high loads. Fiber glass shows moderate performance for 50 μm fineness and lower performance for 25 μm fineness. Cotton exhibits low performance, while the acrylic / phenolic resin exhibits the worst performance. The measurement according to FIG. 1 is carried out before the (primary) hydrogenation step.

FIG. 2 shows the total water content according to the mass flow through the cartridge before the secondary hydrogenation step, with the first hydrogenation step already carried out before the measurement. While metals still show the best coalescing performance, the performance of fiber glass is reduced compared to that before the first hydrogenation step.

Claims (16)

A method of reducing the water content in pyrolysis gasoline obtained from the steam cracking step, characterized in that the water is separated from the pyrolysis gasoline through at least one coalescer made of metal, fiber glass or a combination of metal and fiber glass. How to. The method of claim 1,
A coalescer is used before the hydrogenation step, characterized in that the hydrogenation step is preferably a primary hydrogenation step. 3. The method according to claim 1 or 2,
A coalescer is used after the phase separation step, wherein the main phase water is separated from the pyrolysis gasoline. The method of claim 3, wherein
Wherein the pyrolysis gasoline contains up to 3% by weight of water, preferably 0.3 to 2.5% by weight of water after the phase separation step. The method according to claim 3 or 4,
Characterized in that the phase separation step is carried out in a phase separation unit selected from the group consisting of a charge or filler, a network, a centrifuge, a separator or a settler with a membrane, a vessel and a column. 6. The method according to any one of claims 1 to 5,
A coalescer is a coalescing filter cartridge, coalescing filter or coalescing tube. 7. The method according to any one of claims 1 to 6,
The coalescer further comprises a filler material, wherein the material is preferably made of the same material as the coalescer. The method according to any one of claims 1 to 7,
Characterized in that the water separation in the coalescer is carried out at a temperature below 40 ° C. of the pyrolysis gasoline. The method according to any one of claims 1 to 8,
(a) quenching the pyrolysis gasoline mixture;
(b) phase separation from the pyrolysis gasoline by separation of water as the main phase;
(c) causing the pyrolysis gasoline to contain up to 3% by weight of water through the coalescer;
(d) applying the entrained water-free pyrolysis gasoline to the hydrogenation step
≪ / RTI > 10. The method according to any one of claims 1 to 9,
The coalescer is a coalescer (A) used before the primary hydrogenation step and / or the coalescer is a coalescer (B) used before the secondary hydrogenation step. 11. The method of claim 10,
The coalescer (A) is made of metal and / or the coalescer (B) is made of metal. 10. The method according to any one of claims 1 to 9,
A method wherein the coalescer (A) is used before the secondary hydrogenation step and the coalescer (B), which can be made of any material, is used before the primary hydrogenation step. An apparatus comprising at least one coalescer, a water separation unit and at least one hydrogenation unit made of metal, fiber glass or a combination of metal and fiber glass. The method of claim 13,
A water separation unit is connected to the coalescer (A) and the coalescer (A) is connected to the primary hydrogenation unit, the primary hydrogenation unit is connected to the coalescer (B), followed by a secondary hydrogen unit, and A device in which a coalescer (A) and / or a coalescer (B) is made of metal, fiber glass or a combination of metal and fiber glass. Use of the device according to claim 13 or 14 for the water separation of pyrolysis gasoline. The method of claim 15,
Use characterized in that the coalescer is made of metal.

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